如何从项目列表中获取 substring 并将 substring 值分配给 C# 中的同一项目

Question

StartTime	AgentId
08/19/2021 07:04:56 AM UTC	33
08/11/2021 02:58:35 PM IST	42
08/12/2021 01:01:51 AM CST	24
08/12/2021 08:52:34 PM UTC	61

public class MyModel
{
  public string  StartTime { get; set; }
  public int      AgentId   { get; set; }
  public string   TimeZone  { get; set; }
  public string   Time      { get; set; }
}

I have the above C# Class model MyModel and its sample data stored as a List<MyModel> in my logic. I need a help to parse the StartTime field of a list such that, the TimeZone field should get the UTC/CST/IST of its corresponding StartTime and Time field of a list should be time stamp from its StartTime i,e: 07:04:56 or 02:58:35 and so on. Finally the list should look like something like below:

StartTime	AgentId	Time	TimeZone
08/19/2021 07:04:56 AM UTC	33	07:04:56 AM	UTC
08/11/2021 02:58:35 PM IST	42	02:58:35 PM	IST
08/12/2021 01:01:51 AM CST	24	01:01:51 AM	CST
08/12/2021 08:52:34 PM UTC	61	08:52:34 PM	UTC

Answer 1

Given the fact that all of the segments in your StartTime property have a forced amount of characters thanks to the string format (except for the timezone where we could have eg CEST but that doesn't matter since it's the last segment and I'll get to the why later) we can simply use the String.Substring method and for the first parameter, define the character from where the newly to be output string should start reading and as the second parameter, the amount of characters it should read from there on out.

With that in mind I adjusted your class to this:

public class MyModel
{
    public string StartTime { get; set; }
    public int AgentId { get; set; }
    public string TimeZone => this.StartTime.Substring(23);
    public string Time => this.StartTime.Substring(11, 11);
}

For the TimeZone property you can see that we only passed one parameter. The default behaviour for not passing the second parameter simply means "start reading at index of the parameter and read the string to its end" which is also why a different amount of possible characters in the timezone is nothing we have to worry about.

The way this solution works is, whenever you access either the TimeZone or Time property, the code will be executed returning the substring that you need. Performance wise there would be a disadvantage where the code would be executed every time you call either of the properties even when the StartTime value hasn't changed.

Alternatively you could do it the other way around where every time you pass a new value to the StartTime both of the properties would be updated as well:

public class MyModel
{
    private string _startTime;
    public string StartTime
    {
        get => _startTime;
        set
        {
            this._startTime = value;
            this.TimeZone = value.Substring(23);
            this.Time = value.Substring(11, 11);
        }
    }

    public int AgentId { get; set; }
    public string TimeZone { get; private set; }
    public string Time { get; private set; }
}

This eliminates previously mentioned disadvantage but creates a new one where the TimeZone and Time property will always be updated whenever the StartTime property is, even if you wouldn't use it.

Personally, I'd stick to the first option simply because it's shorter and easier to read.

Answer 2

You can use this sample and run code in this link :

class Program
    {
        static void Main(string[] args)
        {
            var list = new List<string>
            {
                "08/19/2021 07:04:56 AM UTC ",
                "08/11/2021 02:58:35 PM IST ",
                "08/12/2021 01:01:51 AM CST ",
                "08/12/2021 08:52:34 PM UTC "
            };

            var list2 = new List<DateInfo>();
            list.ForEach(e =>
            {
                e = e.Trim();
                var dt = DateTime.Parse(e.Substring(0, e.Length - 3)).Date;
                var tm = DateTime.Parse(e.Substring(0, e.Length - 3)).TimeOfDay;
                list2.Add(new DateInfo
                {
                    StartTime = dt,
                    Time = tm,
                    TimeZone = e[^3..]
                });
            });

            list2.ForEach(e =>
            {
                Console.WriteLine(e.ToString());
            });


        }
    }


    public class DateInfo
    {
        public DateTime StartTime { get; set; }
        public TimeSpan Time { get; set; }
        public string TimeZone { get; set; }

        public override string ToString()
        {
            return ($"StartTime : {StartTime:yyyy/MM/dd}, Time : {Time}, TimeZone : {TimeZone}");
        }

    }